Multibeam inspection apparatus

ABSTRACT

A pattern inspection apparatus according to an aspect described herein includes: a stage on which an object to be inspected is capable to be mounted, a multibeam column that irradiates the object to be inspected with multi-primary electron beams, and a multi-detector including a first detection pixel that receives irradiation of a first secondary electron beam emitted after a first beam scanning region of the object to be inspected is irradiated with a first primary electron beam of the multi-primary electron beams and a second detection pixel that receives irradiation of a second secondary electron beam emitted after a second beam scanning region adjacent to the first beam scanning region of the object to be inspected and overlapping with the first beam scanning region is irradiated with a second primary electron beam adjacent to the first primary electron beam of the multi-primary electron beams; a comparison unit that obtains a difference in beam intensity between the first primary electron beam and the second primary electron beam by comparing overlapping portions of a first frame image acquired through entering of the first secondary electron beam into the first detection pixel and a second frame image acquired through entering of the second secondary electron beam into the second detection pixel; and a sensitivity adjustor that adjusts detection sensitivity of the first detection pixel and/or the second detection pixel so as to correct the difference in beam intensity.

CROSS-REFERENCE TO RELATED APPLICATION

This application is based upon and claims the benefit of priority fromJapanese Patent Applications No. 2019-111579, filed on Jun. 14, 2019,the entire contents of which are incorporated herein by reference.

FIELD OF THE INVENTION

Embodiments described herein relate generally to a multibeam inspectionapparatus. For example, the embodiments described herein relate to aninspection apparatus that acquires a secondary electron image of apattern emitted through irradiation of a multibeam by an electron beamso as to inspect the pattern.

BACKGROUND OF THE INVENTION

In recent years, due to an increase in a degree of integration and acapacity of large scale integration (LSI), widths of circuit linesrequired for semiconductor elements have gotten narrower and narrower.These semiconductor elements are manufactured by circuit formationthrough transfer exposure of a pattern on a wafer by a reductionprojection exposure apparatus, which is a so-called stepper, using anoriginal pattern (also called a mask or a reticle. Hereinafter,collectively called a mask) in which a circuit pattern is formed.

For manufacturing LSI that requires a large manufacturing cost, it isindispensable to improve yield. A pattern that constitutes LSI is in ananometer order. In recent years, due to miniaturization of a size of anLSI pattern formed on a semiconductor wafer, a size that needs to bedetected as a pattern defect has been very small. Therefore, it isnecessary to enhance the accuracy of a pattern inspection apparatus forinspecting a defect of an ultrafine pattern transferred on asemiconductor wafer. Other than that, as one of the major factorscontributing to a decrease in the yield is a pattern defect of a maskused for exposure and transfer of an ultrafine pattern on asemiconductor wafer by a photolithography technique. Therefore, it isnecessary to enhance the accuracy of a pattern inspection apparatus forinspecting a defect of a mask for transfer used for manufacturing LSI.

An inspection method that has been known is a method for performing aninspection through a comparison between an optical image obtained bycapturing a pattern formed on a sample such as a semiconductor wafer ora lithography mask at a prescribed magnification using a magnifyingoptical system, and design data or an optical image obtained bycapturing an identical pattern on the sample. Examples of the patterninspection method include a “die to die inspection” that comparesoptical image data obtained by capturing identical patterns in differentlocations on the same mask, and a “die to database inspection” thatgenerates design image data (reference image) simulating an opticalimage based on a computer-aided design (CAD) pattern format for adrawing apparatus, and then compares this design image data (referencedata) with an optical image serving as measurement data obtained bycapturing the pattern. In the inspection method of the inspectionapparatus, a substrate to be inspected is placed on a stage and aluminous flux performs scanning on the sample as the stage moves so asto perform an inspection. The luminous flux is irradiated on thesubstrate to be inspected by a light source and an illumination opticalsystem. An image of light that penetrates or is reflected by thesubstrate to be inspected is formed on a sensor via an optical system.The image captured by the sensor is sent to a comparison unit asmeasurement data. In the comparison unit, after positions of images arematched, the measurement data and reference data are compared with eachother according to an appropriate algorithm. When matching does notsucceed, it is determined that a pattern defect exists.

The pattern inspection apparatus described above acquires an opticalimage by irradiating the substrate to be inspected with a laser beam andcapturing this transmitted image or reflected image. On the other hand,an inspection apparatus has been developed that irradiates a substrateto be inspected with a multibeam formed of a plurality of electron beamsin an array in which a plurality of beam rows arrayed on a straight lineat the same pitch is arranged, and detects a secondary electroncorresponding to each beam emitted from the substrate to be inspected toacquire a pattern image. The pattern inspection apparatus using theelectron beam including the multibeam detects the secondary electron byperforming scanning for each small region of the substrate to beinspected. At this time, a so-called step and repeat operation isperformed in which the position of the substrate to be inspected isfixed during beam scanning, and the position of the substrate to beinspected is moved to a next small region after the scanning ends.Through using of a multibeam in an array in which a plurality of beamrows arrayed on a straight line at the same pitch is arranged, multiplebeams can be disposed in a limited region. This enables simultaneousscanning of multiple small regions at a time. As a result, improvementof throughput is expected.

In JP 2017-090063 A, it is described that in the pattern inspectionapparatus of multibeam type, n₁×m₁ irradiation unit regions in atwo-dimensional state in each image reference region are irradiated witha plurality of different beams of a multibeam.

SUMMARY OF THE INVENTION

A pattern inspection apparatus according to an aspect described hereinincludes: a stage on which an object to be inspected is capable to bemounted, a multibeam column that irradiates the object to be inspectedwith multi-primary electron beams, and a multi-detector including afirst detection pixel that receives irradiation of a first secondaryelectron beam emitted after a first beam scanning region of the objectto be inspected is irradiated with a first primary electron beam of themulti-primary electron beams and a second detection pixel that receivesirradiation of a second secondary electron beam emitted after a secondbeam scanning region adjacent to the first beam scanning region of theobject to be inspected and overlapping with a first scanning region isirradiated with a second primary electron beam adjacent to the firstprimary electron beam of the multi-primary electron beams; a comparisonunit that obtains a difference in beam intensity between the firstprimary electron beam and the second primary electron beam by comparingoverlapping portions of a first frame image acquired through entering ofthe first secondary electron beam into the first detection pixel and asecond frame image acquired through entering of the second secondaryelectron beam into the second detection pixel; and a sensitivityadjustor that adjusts detection sensitivity of the first detection pixeland/or the second detection pixel so as to correct the difference inbeam intensity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a configuration diagram showing a configuration of a multibeaminspection apparatus according to a first embodiment;

FIG. 2 is a schematic view showing a configuration of a shaping aperturearray substrate according to the first embodiment;

FIG. 3 is a schematic view showing a first beam scanning region A1, asecond beam scanning region A2, a third beam scanning region A3, afourth beam scanning region A4, a fifth beam scanning region A5, a sixthbeam scanning region A6, a seventh beam scanning region A7, an eighthbeam scanning region A8, and a ninth beam scanning region A9 accordingto the first embodiment;

FIG. 4 is a schematic view showing a first frame image C1, a secondframe image C2, a third frame image C3, a fourth frame image C4, a fifthframe image C5, a sixth frame image C6, a seventh frame image C7, aneighth frame image C8, and a ninth frame image C9 according to the firstembodiment;

FIG. 5 is a schematic view showing a position deviation compensationarea, a non-effective region portion caused by image processing, and aneffective region of one beam scanning region according to the firstembodiment;

FIG. 6 is a schematic view showing a width overlapping with an adjacentinspection area according to the first embodiment;

FIG. 7 is a flowchart of a multibeam inspection method according to thefirst embodiment;

FIG. 8 is a flowchart of the multibeam inspection method according tothe first embodiment;

FIG. 9 is a flowchart of a multibeam inspection method according to asecond embodiment;

FIG. 10 is a flowchart of the multibeam inspection method according tothe second embodiment;

FIG. 11 is a flowchart of a multibeam inspection method according to athird embodiment;

FIG. 12 is a flowchart of the multibeam inspection method according tothe third embodiment; and

FIG. 13 is a schematic view of the pixel B, which is common to the firstframe image C1 and the second frame image C2 according to a fourthembodiment.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments described herein will be explained withreference to the drawings.

Hereinafter, in the embodiments, a case where an electron beam is usedas an example of a charged particle beam will be explained. However, thecharged particle beam is not limited thereto. Another charged particlebeam such as an ion beam may be used.

A pattern inspection apparatus according to an aspect described hereinincludes: a stage on which an object to be inspected is capable to bemounted, a multibeam column that irradiates the object to be inspectedwith multi-primary electron beams, and a multi-detector including afirst detection pixel that receives irradiation of a first secondaryelectron beam emitted after a first beam scanning region of the objectto be inspected is irradiated with a first primary electron beam of themulti-primary electron beams and a second detection pixel that receivesirradiation of a second secondary electron beam emitted after a secondbeam scanning region adjacent to the first beam scanning region of theobject to be inspected and overlapping with the first beam scanningregion is irradiated with a second primary electron beam adjacent to thefirst primary electron beam of the multi-primary electron beams; acomparison unit that obtains a difference in beam intensity between thefirst primary electron beam and the second primary electron beam bycomparing overlapping portions of a first frame image acquired throughentering of the first secondary electron beam into the first detectionpixel and a second frame image acquired through entering of the secondsecondary electron beam into the second detection pixel; and asensitivity adjustor that adjusts detection sensitivity of the firstdetection pixel and/or the second detection pixel so as to correct thedifference in beam intensity.

First Embodiment

FIG. 1 is a configuration diagram showing a configuration of a patterninspection apparatus according to a first embodiment. In FIG. 1, aninspection apparatus 100 that inspects a pattern formed on a substrateis one example of a charged particle beam inspection apparatus. Theinspection apparatus 100 includes a controller 110 and anelectronic-optical image acquisition mechanism 150. The controller 110includes a control computer 121, a bus 122, a storage device 131, amonitor 132, a printer 133, a memory 134, a position calculator 135, astage controller 136, a deflection controller 137, a blanking controller138, a lens controller 139, an inspection image creation unit 140, acomparison unit 141, a sensitivity adjustor 142, an image corrector 143,and a reference image creation unit 144. The electronic-optical imageacquisition mechanism 150 includes a driving unit 151, a laser lengthmeasuring system 152, a detector 153, a pattern memory 154, an electronbeam column 161 (electronic lens barrel), and an inspection chamber 162.In the electron beam column 161, an electron gun 163, an illuminationlens 164, a shaping aperture array substrate 165, a reducing lens 166, alimit aperture substrate 167, an objective lens 168, a main deflector169, a sub-reflector 170, a collectively blanking deflector 171, a beamseparator 172, a projection lens 173, a projection lens 174, a deflector175, and a multi-detector 176 are disposed.

In the inspection chamber 162, for example, a stage 177 and a mirror 178capable of moving on an xy plane are disposed. On the stage 177, anobject to be inspected including a region to be inspected X is disposed.Examples of the object to be inspected include a semiconductorsubstrate, a chip in which a pattern is formed, and a mask for forming apattern. The object to be inspected X is disposed with a patternformation surface facing upward on the stage 177. Moreover, on the stage177, the mirror 178 is disposed that reflects a laser beam for measuringa length of laser irradiated from the laser length measuring system 152disposed outside the inspection chamber 162.

The multi-detector 176 is connected to the detector 153 outside theelectron beam column 161. The detector 153 is connected to the patternmemory 154.

In the controller 110, the control computer 121 that serves as acomputer is connected to the storage device 131, the monitor 132, theprinter 133, the memory 134, the position calculator 135, the stagecontroller 136, the deflection controller 137, the blanking controller138, the lens controller 139, the inspection image creation unit 140,the comparison unit 141, the sensitivity adjustor 142, the imagecorrector 143, and the reference image creation unit 144 through the bus122. Moreover, the pattern memory 154 is connected to the inspectionimage creation unit 140.

In the stage 177, the stage controller 136 controls the driving unit151. The driving unit 151 controlled by the stage controller 136 movesthe position of the stage 177. The driving unit 151 is configured bydriving systems such as motors of three axes (x-y-θ) that cause drivingin an x-direction, a y-direction, and a θ direction. These drivingsystems enable the stage 177 to move in an arbitrary direction. Forthese x-motor, y-motor, and θ-motor, which are not shown, a step motorcan be used, for example. The stage 177 can move in a horizontaldirection and a rotation direction by the motor of each of x-, y- andθ-axes. A moving position of the stage 177 is measured by the laserlength measuring system 152 and provided to the position calculator 135,and positions of the stage 177 and the region to be inspected X arecalculated. The laser length measuring system 152 measures the positionof the stage 177 according to the principle of laser interferometry byreceiving reflection light from the mirror 178, for example.

A high-voltage power supply circuit, which is not shown, is connected tothe electron gun 163. Together with application of acceleration voltagebetween a filament and an extraction electrode, which are not shown, inthe electron gun 163 from the high-voltage supply circuit, applicationof voltage of a prescribed extraction electrode and heating of a cathode(filament) at a prescribed temperature cause acceleration of an electrongroup emitted from the cathode, followed by emission as electron beams.For example, an electromagnetic lens is used for the illumination lens164, the reducing lens 166, the objective lens 168, the projection lens173, and the projection lens 174, and the lens controller 139 controlsthese lenses. Moreover, the lens controller 139 also controls the beamseparator 172. The collectively blanking deflector 171 and the deflector175 are each configured by an electrode group having at least twoelectrodes, and controlled by the blanking controller 138. The maindeflector 169 and the sub-reflector 170 are each configured by anelectrode group having at least four electrodes, and controlled by thedeflection controller 137.

When the region to be inspected X is a semiconductor wafer in which aplurality of chip (die) patterns is formed, pattern data of the chip(die) patterns is input from the outside of the inspection apparatus 100and stored in the storage device 131. When the region to be inspected Xis a mask for exposure, design pattern data based on which a maskpattern is formed on the mask for exposure is input from the outside ofthe inspection apparatus 100 and stored in the storage device 131.

Here, in FIG. 1, a configuration necessary for explanation of the firstembodiment is described. Other configurations normally necessary for theinspection apparatus 100 may be included.

FIG. 2 is a schematic view showing a configuration of a shaping aperturearray substrate 165 according to the first embodiment. In FIG. 2, in theshaping aperture array substrate 165, holes (openings) A in M horizontalrows (x-direction)×M′ vertical steps (y-direction) in a two-dimensionalstate (matrix), where M is an integer of 2 or larger, and M′ is aninteger of 1 or larger, are formed at a prescribed array pitch L in anx-direction and a y-direction (x: a first direction, y: a seconddirection). Note that when a reduction magnification of the multibeam isA (when a diameter of the multibeam is reduced to 1/A to irradiate theregion to be inspected X), and a pitch between beams of the multibeamwith respect to the x- and y-directions on a sample 101 is p, the arraypitch L satisfies a relation of L=(A×p). The example of FIG. 2 shows acase where holes 22 are formed for forming 5×5 beams of the multibeam,where M is 5 and M′ is 5. Next, an operation of the electronic-opticalimage acquisition mechanism 150 in the inspection apparatus 100 will beexplained.

An electron beam 201 emitted from the electron gun 163 (emission source)substantially vertically illuminates the entire shaping aperture arraysubstrate 165 by the illumination lens 164. In the shaping aperturearray substrate 165, as shown in FIG. 2, a plurality of holes 22(openings) having a rectangular shape is formed, and the electron beam201 illuminates a region including all of the plurality of holes 22.Since each part of the electron beam 201 irradiated in a position of theplurality of holes 22 passes through each of the plurality of holes 22of the shaping aperture array substrate 165, for example, a plurality ofelectron beams (multibeam) 202 a, 202 b, 202 c, and 202 d having arectangular shape (solid lines in FIG. 1) (multi-primary electron beams)is formed.

After passing through the beam separator 172, the formed multi-primaryelectron beams 202 a to 202 d are reduced by the reducing lens 166, andtravel toward a center hole formed in the limit aperture substrate 167.Here, when the entire multi-primary electron beams 202 a to 202 d havebeen collectively deflected by the collectively blanking deflector 171disposed between the shaping aperture array substrate 165 and thereducing lens 166, the multi-primary electron beams 202 a to 202 dpositionally deviate from the center hole of the limit aperturesubstrate 167, and are shielded by the limit aperture substrate 167. Onthe other hand, the multi-primary electron beams 202 a to 202 d thathave not been deflected by the collectively blanking deflector 171 passthrough the center hole of the limit aperture substrate 167 as shown inFIG. 1. According to an on/off state of the collectively blankingdeflector 171, blanking is controlled and the on/off state of the beamsare collectively controlled. In this way, the limit aperture substrate167 shields the multi-primary electron beams 202 a to 202 d that havebeen deflected by the collectively blanking deflector 171 to enter thebeam-off state A beam group that have been formed from the beam-on stateto the beam-off state and passed through the limit aperture substrate167 forms the multi-primary electron beams 202 a to 202 d forinspection.

The multi-primary electron beams 202 a to 202 d that have passed throughthe limit aperture substrate 167 are focused on a surface of the regionto be inspected X by the objective lens 168, become pattern images (beamdiameter) having a desired reduction rate. The entire multi-primaryelectron beams 202 that have passed through the limit aperture substrate167 are collectively deflected in the same direction by the maindeflector 169 and the sub-reflector 170, and irradiated in a respectiveirradiation position on the region to be inspected X of each beam. Inthis case, the main deflector 169 collectively deflects the entiremulti-primary electron beams 202 in reference positions of the region tobe inspected X to be scanned by the multi-primary electron beams 202.

In the first embodiment, for example, scanning is performed while thestage 177 is continuously moved. Therefore, the main deflector 169performs tracking deflection so as to follow the movement of the stage177. Then, the sub-reflector 170 collectively deflects the entiremulti-primary electron beams 202 so that each beam performs scanning ina region that each beam corresponds to. The multi-primary electron beams202 irradiated at one time are arranged ideally at a pitch obtainedthrough multiplying of an array pitch of the plurality of holes 22 ofthe shaping aperture array substrate 165 by the desired reduction rate(1/A) described above. In this way, the electron beam column 161irradiates the region to be inspected X with m₁×n₁ beams of themulti-primary electron beams 202 in the two-dimensional state at a time.As a result of irradiation of the multi-primary electron beams 202 indesired positions of the region to be inspected X, a flux of secondaryelectrons (multi-secondary electron beams 203 a, 203 b, 203 c, and 203d) (broken lines in FIG. 1) is emitted from the region to be inspectedX, the flux of secondary electrons corresponding to each beam of themulti-primary electron beams 202 and including reflection electrons.

Multi-secondary electron beams 203 emitted from the region to beinspected X are refracted by the objective lens 168 on a side of acenter of the multi-secondary electron beams 203, and travel toward thecenter hole formed in the limit aperture substrate 167. Themulti-secondary electron beams 203 that have passed the limit aperturesubstrate 167 are refracted by the reducing lens 166 in substantiallyparallel to an optical axis, and travel toward the beam separator 172.

Here, the beam separator 172 generates an electric field and a magneticfield in an orthogonal direction on a surface orthogonal to a direction(optical axis) toward which the multi-primary electron beams 202 travel.The electric field exerts a force in the same direction regardless of atravelling direction of electrons. On the other hand, the magnetic fieldexerts a force according to the Fleming's left-hand rule. Accordingly, adirection of a force applied to the electrons can be changed by an entrydirection of the electrons. For the multi-primary electron beams 202(primary electron beams) that enter the beam separator 172 from above,the force by the electric field and the force by the magnetic fieldcancel each other, and the multi-primary electron beams 202 movestraight down. On the other hand, for the multi-secondary electron beams203 that enter the beam separator 172 from below, the force by theelectric field and the force by the magnetic field both work in the samedirection, and the multi-secondary electron beams 203 are bent obliquelyupward.

The multi-secondary electron beams 203 bent obliquely upward areprojected onto the multi-detector 176 while being refracted by theprojection lens 173 and the projection lens 174. The multi-detector 176detects the projected multi-secondary electron beams 203. Themulti-detector 176 includes a plurality of detection pixels. Themulti-detector 176 includes, for example, a two-dimensional sensor ofdiode type, which is not shown. Then, in a position of thetwo-dimensional sensor of diode type corresponding to each beam of themulti-secondary electron beams 203, each secondary electron of themulti-secondary electron beams 203 collides with the two-dimensionalsensor of diode type, generates electrons, and generates secondaryelectron image data for each pixel described later. Moreover, scanningis performed while the stage 177 is continuously moved, the trackingdeflection is performed as described above. In response to the movementof the deflection position associated with the tracking deflection, thedeflector 175 deflects the multi-secondary electron beams 203 so as toirradiate a desired position on a light-receiving surface of themulti-detector 176.

FIG. 3 is a schematic view describing a first beam scanning region A1, asecond beam scanning region A2, a third beam scanning region A3, afourth beam scanning region A4, a fifth beam scanning region A5, a sixthbeam scanning region A6, a seventh beam scanning region A7, an eighthbeam scanning region A8, and a ninth beam scanning region A9 accordingto the embodiment. FIG. 3 shows regions to be scanned by themulti-primary electron beams 202 in the region to be inspected X. Forexample, when the region to be inspected X is inspected by nine beams ofthe multi-primary electron beams 202 in 3×3, a process for inspecting asub-inspection region including 3×3 scanning regions is performed aplurality of times so as to inspect the entire region to be inspected X.In the embodiment, for the sake of convenience, the nine scanningregions are shown and explained. Therefore, FIG. 4 also shows nineoutput images C1 to C9 corresponding to scanning regions A1 to A9. Theseare examples, and the number of holes 22, the number of multi-primaryelectron beams 202, the number of scanning regions, the number of pixelsof the multi-detector 176, and the like are not limited thereto.

FIG. 3 shows the scanning regions A1 to A9 of the multi-primary electronbeams 202 and overlapping regions B1 to B12 of the scanning regions A1to A9 in the region to be inspected X. An region occupied by the firstto ninth beam scanning regions A1 to A9 are a part of the region to beinspected X. Each scanning region is distinguished by a hatchingpattern. A part in which hatching patterns overlap with each other is aregion in which scanning regions overlap with each other. An n-thprimary electron beam, which is one beam of the multi-primary electronbeams 202, is defined as the n-th primary electron beam 202. The area tobe scanned by the first primary electron beam 202 is the first beamscanning region A1. The area to be scanned by the second primaryelectron beam 202 is the second beam scanning region A2. The area to bescanned by the third primary electron beam 202 is the third beamscanning region A3. The area to be scanned by the fourth primaryelectron beam 202 is the fourth beam scanning region A4. The area to bescanned by the fifth primary electron beam 202 is the fifth beamscanning region A5. The area to be scanned by the sixth primary electronbeam 202 is the sixth beam scanning region A6. The area to be scanned bythe seventh primary electron beam 202 is the seventh beam scanningregion A7. The area to be scanned by the eighth primary electron beam202 is the eighth beam scanning region A8. The area to be scanned by theninth primary electron beam 202 is the ninth beam scanning region A9.

The first primary electron beam 202 is adjacent to the second primaryelectron beam 202, the fourth primary electron beam 202, and the fifthprimary electron beam 202. The second primary electron beam 202 isadjacent to the first primary electron beam 202, the third primaryelectron beam 202, the fourth primary electron beam 202, the fifthprimary electron beam 202, and the sixth primary electron beam 202. Thethird primary electron beam 202 is adjacent to the second primaryelectron beam 202, the fifth primary electron beam 202, and the sixthprimary electron beam 202. The fourth primary electron beam 202 isadjacent to the first primary electron beam 202, the second primaryelectron beam 202, the fifth primary electron beam 202, the seventhprimary electron beam 202, and the eighth primary electron beam 202. Thefifth primary electron beam 202 is adjacent to the first primaryelectron beam 202, the second primary electron beam 202, the thirdprimary electron beam 202, the fourth primary electron beam 202, thesixth primary electron beam 202, the seventh primary electron beam 202,the eighth primary electron beam 202, and the ninth primary electronbeam 202. The sixth primary electron beam 202 is adjacent to the secondprimary electron beam 202, the third primary electron beam 202, thefifth primary electron beam 202, the eighth primary electron beam 202,and the ninth primary electron beam 202. The seventh primary electronbeam 202 is adjacent to the fourth primary electron beam 202, the fifthprimary electron beam 202, and the eighth primary electron beam 202. Theeighth primary electron beam 202 is adjacent to the fourth primaryelectron beam 202, the fifth primary electron beam 202, the sixthprimary electron beam 202, the seventh primary electron beam 202, andthe ninth primary electron beam 202. The ninth primary electron beam 202is adjacent to the fifth primary electron beam 202, the sixth primaryelectron beam 202, and the eighth primary electron beam 202.

A positional relation of the adjacent primary electron beams 202corresponds to a positional relation of the adjacent scanning regionseach of which is to be scanned by each beam. Numbers of the beams alsocorrespond to numbers of the scanning regions. For example, the firstbeam scanning region A1 is adjacent to the second beam scanning regionA2, the fourth beam scanning region A4, and the fifth beam scanningregion A5.

In order to prevent omission of an inspection area, when a positiondeviation of each beam scanning region caused by apparatus performanceis taken into consideration, and in addition, output imagescorresponding to the respective beams are treated with image processingusing peripheral pixels such as blur processing, an non-effective regionaccording to calculation processing is generated in an image endportion. Therefore, it is necessary to add the amount of thenon-effective region as needed and set the scanning regions to bescanned by the adjacent primary electron beams 202 so as to overlap withthe scanning regions of the electron beams having the adjacency relationexplained earlier. FIG. 5 is a view schematically showing a positiondeviation compensation area T1, a non-effective region portion T2 causedby image processing, and an effective region T3 of one beam scanningregion. FIG. 6 schematically shows a width overlapping with an adjacentinspection area. As shown in FIG. 6, a width T4 overlapping with theadjacent inspection area needs to be set toT4>(width of T1+width of T2)×2

so as to overlap with an inspection effective region of the adjacentarea.

An overlapping scanning region B1 is a region in which the first beamscanning region A1 and the second beam scanning region A2 adjacent tothe first beam scanning region A1 overlap with each other. Anoverlapping scanning region B2 is a region in which the second beamscanning region A2 and the third beam scanning region A3 adjacent to thesecond beam scanning region A2 overlap with each other. An overlappingscanning region B3 is a region in which the first beam scanning regionA1 and the fourth beam scanning region A4 adjacent to the first beamscanning region A1 overlap with each other. An overlapping scanningregion B4 is a region in which the second beam scanning region A2 andthe fifth beam scanning region A5 adjacent to the second beam scanningregion A2 overlap with each other. An overlapping scanning region B5 isa region in which the third beam scanning region A3 and the sixth beamscanning region A6 adjacent to the third beam scanning region A3 overlapwith each other. An overlapping scanning region B6 is a region in whichthe fourth beam scanning region A4 and the fifth beam scanning region A5adjacent to the fourth beam scanning region A4 overlap with each other.An overlapping scanning region B7 is a region in which the fifth beamscanning region A5 and the sixth beam scanning region A6 adjacent to thefifth beam scanning region A5 overlap with each other. An overlappingscanning region B8 is a region in which the fourth beam scanning regionA4 and the seventh beam scanning region A7 adjacent to the fourth beamscanning region A4 overlap with each other. An overlapping scanningregion B9 is a region in which the fifth beam scanning region A5 and theeighth beam scanning region A8 adjacent to the fifth beam scanningregion A5 overlap with each other. An overlapping scanning region B10 isa region in which the sixth beam scanning region A6 and the ninth beamscanning region A9 adjacent to the sixth beam scanning region A6 overlapwith each other. An overlapping scanning region B11 is a region in whichthe seventh beam scanning region A7 and the eighth beam scanning regionA8 adjacent to the seventh beam scanning region A7 overlap with eachother. An overlapping scanning region B12 is a region in which theeighth beam scanning region A8 and the ninth beam scanning region A9adjacent to the eighth beam scanning region A8 overlap with each other.Note that, for example, the overlapping scanning region B1 also includesa region in which the first beam scanning region A1 and the fifth beamscanning region A5 overlap with each other (a region in which fouroverlapping regions, which are the overlapping region B1, theoverlapping region B3, the overlapping region B4, and the overlappingregion B6, overlap with each other).

Hereinafter, an image processing unit of an image acquired by asecondary electron beam output through electron beam scanning in theapparatus is called a frame. A size of the frame may be processed afterbeing divided into a plurality of parts within an output image from eachelectron beam scanning region. Regarding a necessary overlapping amountof the adjacent electron beam scanning regions explained above, even ifthe size of the frame is divided into the plurality of parts in eachelectron beam scanning region, the width of a non-effective regiongenerated by image processing in the end portion of the beam scanningregion is the same, and thus for convenience of explanation of examples,an explanation will be given assuming that the size of the output imageacquired from each electron beam scanning region matches one frame imagein the image processing unit.

FIG. 4 is a schematic view for explaining a first frame image C1, asecond frame image C2, a third frame image C3, a fourth frame image C4,a fifth frame image C5, a sixth frame image C6, a seventh frame imageC7, an eighth frame image C8, and a ninth frame image C9 according tothe embodiment. A sub-inspection region image is acquired throughjoining of vertical 3 frame images×horizontal 3 frame images so that theframe images partially overlap with each other. An inspection regionimage Y can be acquired through further overlapping and joining of thesub-inspection region images. When the number of sub-inspection regionis one, the sub-inspection region image serves as the inspection regionimage Y. FIG. 4 shows a region of the inspection region image Y acquiredfrom the secondary electron beam 203 emitted from each scanning regionof the region to be inspected X. Numbers of the scanning regionscorrespond to numbers of the frame images.

Through irradiation of the region to be inspected X with themulti-primary electron beams 202, the multi-secondary electron beams 203emitted from the region to be inspected X enter the multi-detector 176as described above. The multi-secondary electron beams 203 emittedthrough illumination of each scanning region (for example, scanningregions A1 to A9 in FIG. 3) each enters a different pixel in themulti-detector 176. Based on data of intensity and an inspectionposition of the secondary electron beam 203 that has entered each pixeland, the frame image of each scanning region is created. Note that thefirst detection pixel may be one detection pixel, or may be formed of aplurality of sub-pixels disposed in a two-dimensional state.

FIG. 4 shows the frame images C1 to C9 created from each of themulti-secondary electron beams 203 within the inspection region image Y,first to twelfth overlapping frame image regions D1 to D12 of the frameimages C1 to C9. A signal of the secondary electron beam 203 enteringthe multi-detector 176 is processed in the detector 153. For example, ananalogue signal input into the detector 153 is converted into a digitalsignal. Processing such as amplifying can be performed before and afterconversion of a signal. The digital signal generated by the processingin the detector 153 is temporarily stored in the pattern memory 154, anda frame image necessary for an inspection is created from data stored inthe pattern memory 154 in the inspection image creation unit 140.

The first secondary electron beam 203 emitted from the first scanningregion A1 enters a first detection pixel of the multi-detector 176 so asto acquire the first frame image C1. Moreover, the second secondaryelectron beam 203 adjacent to the first secondary electron beam 203enters a second detection pixel adjacent to the first detection pixel ofthe multi-detector 176 so as to acquire the second frame image C2.Moreover, the third secondary electron beam 203 adjacent to the secondsecondary electron beam 203 enters a third detection pixel adjacent tothe second detection pixel of the multi-detector 176 so as to acquirethe third frame image C3. Moreover, the fourth secondary electron beam203 adjacent to the first secondary electron beam 203 enters a fourthdetection pixel adjacent to the first detection pixel of themulti-detector 176 so as to acquire the fourth frame image C4. Moreover,the fifth secondary electron beam 203 adjacent to the fourth secondaryelectron beam 203 enters a fifth detection pixel adjacent to the fourthdetection pixel of the multi-detector 176 so as to acquire the fifthframe image C5. Moreover, the sixth secondary electron beam 203 adjacentto the fifth secondary electron beam 203 enters a sixth detection pixeladjacent to the fifth detection pixel of the multi-detector 176 so as toacquire the sixth frame image C6. Moreover, the seventh secondaryelectron beam 203 adjacent to the fourth secondary electron beam 203enters a seventh detection pixel adjacent to the fourth detection pixelof the multi-detector 176 so as to acquire the seventh frame image C7.Moreover, the eighth secondary electron beam 203 adjacent to the seventhsecondary electron beam 203 enters an eighth detection pixel adjacent tothe seventh detection pixel of the multi-detector 176 so as to acquirethe eighth frame image C8. Moreover, the ninth secondary electron beam203 adjacent to the eighth secondary electron beam 203 enters a ninthdetection pixel adjacent to the eighth detection pixel of themulti-detector 176 so as to acquire the ninth frame image C9.

The acquired frame images C1 to C9 have regions overlapping with theadjacent frame images. The first overlapping frame image region D1 is aregion in which the first frame image C1 and the second frame image C2overlap with each other. The second overlapping frame image region D2 isa region in which the second frame image C2 and the third frame image C3overlap with each other. The third overlapping frame image region D3 isa region in which the first frame image C1 and the fourth frame image C4overlap with each other. The fourth overlapping frame image region D4 isa region in which the second frame image C2 and the fifth frame image C5overlap with each other. The fifth overlapping frame image region D5 isa region in which the third frame image C3 and the sixth frame image C6overlap with each other. The sixth overlapping frame image region D6 isa region in which the fourth frame image C4 and the fifth frame image C5overlap with each other. The seventh overlapping frame image region D7is a region in which the fifth frame image C5 and the sixth frame imageC6 overlap with each other. The eighth overlapping frame image region D8is a region in which the fourth frame image C4 and the seventh frameimage C7 overlap with each other. The ninth overlapping frame imageregion D9 is a region in which the fifth frame image C5 and the eighthframe image C8 overlap with each other. The tenth overlapping frameimage region D10 is a region in which the sixth frame image C6 and theninth frame image C9 overlap with each other. The eleventh overlappingframe image region D11 is a region in which the seventh frame image C7and the eighth frame image C8 overlap with each other. The twelfthoverlapping frame image region D12 is a region in which the eighth frameimage C8 and the ninth frame image C9 overlap with each other. Note thatfor example, the overlapping frame image region D1 also includes aregion in which the first frame image C1 and the fifth frame image C5overlap with each other (a region in which four overlapping regions,which are the overlapping frame image region D1, the overlapping frameimage region D3, the overlapping frame image region D4, and theoverlapping frame image region D6, overlap with each other).

The comparison unit 141 compares a reference frame image generated in areference image creation unit 144 with an inspection frame imagegenerated in an inspection image creation unit 140 (and obtain adifference), and detects a defect from a result of the comparison. Attime of inspection, beam characteristics are calibrated before theinspection so that the difference result in the comparison unit 141 doesnot include a difference in beam characteristics. When a reference frameimage is created in the reference image creation unit, a reference frameimage in which the advance calibration result is incorporated isgenerated, or a correction frame image in which the calibration resultis incorporated is generated in the detector 153 to reduce thedifference by the beam characteristics, and thus only a defective partbecomes a large difference signal and defect detection sensitivity isimproved.

When a change occurs in the beam characteristics due to some causes(such as temperature drift) during an inspection, the change appears asa luminance change of an inspection frame image. However, in imageprocessing of a defect detection operation, the change becomes a changein an offset amount of a difference with the reference frame image.Therefore, when correction of an offset amount between images(correction by a luminance average value), which is generally known, isperformed in the image processing, a large change in the defectdetection sensitivity does not appear, as a result of which this changein the beam characteristics will be missed.

Therefore, in the comparison unit 141 of the embodiment monitors achange (for example, luminance average value) in a portion overlappingwith an adjacent frame image. When there is no change in the intensityof the multi-primary electron beams 202 during an inspection, forexample, the overlapping frame image region D1 in the first frame imageC1 and the overlapping frame image region D1 of the second frame imageC2 are the same image or images having substantially no difference.However, when there is a change in the intensity of the first primaryelectron beam 202 and/or the intensity of the second primary electronbeam 202, the difference between the first frame image C1 in theoverlapping frame image region D1 and the second frame image C2 in theoverlapping frame image region D1 increases. Since the same region ismonitored by the primary electron beams 202 different from each otherusing a different detection pixel, a change between adjacent beams ofthe multi-primary electron beams 202 can be detected.

When a change between the multi-primary electron beams 202 is detected,for example, when a difference in the luminance average value exceeds aset threshold, the sensitivity adjustor 142 calculates an adjustmentamount of detection sensitivity and corrects the detection sensitivityof the detection pixel. Moreover, since the sensitivity adjustor 142 caninstruct the detector 153 to change a signal processing condition in thedetector 153, when a next sub-inspection region is inspected, theinspection can be performed under a condition in which the difference inthe intensity between the multi-primary electron beams 202 has beencorrected, in other words, calibration has been performed again.

After each sub-inspection region is inspected, acquired images arejoined together (partially overlapped) to acquire the inspection regionimage Y. The image corrector 143 may treat the acquired inspectionregion image Y with arbitrary image processing such as removal ofdistortion.

Obtained defect information and inspection images are stored in thestorage device 131, for example.

Next, the inspection apparatus 100 will be explained in more detailthrough an explanation of the inspection method of the multibeaminspection apparatus 100. FIG. 7 shows a flowchart of a multibeaminspection method. An inspection method according to the firstembodiment includes a calibration process (S101), inspection processesof sub-inspection regions (S110 to S1N0), an inspection image creationprocess (S201), a reference image creation process (S202), and acomparison process (S203).

<Calibration Process (S101)>

In the calibration process (S101), the region to be inspected X or asubstrate for calibration is inspected by the multi-primary electronbeams 202, and the detection sensitivity and the like in themulti-detector 176 is adjusted according to the difference in theintensity of the multi-primary electron beams 202. For example, ananalogue signal obtained by the multi-detector 176, a processingcondition of the detector 153 that converts this analogue signal into adigital signal for processing, and the like are changed to adjust thedetection sensitivity.

<Inspection Processes of Sub-Inspection Regions (S110 to S1N0)>

Since a range of the multi-primary electron beams 202 is equal to orless than the inspection range of the region to be inspected X, theregion to be inspected X is divided into at least one sub-inspectionregion, and a plurality of times of inspections from the first to theN-th inspections (N is an integer equal to or more than 1) is performed.An inspection process of a first sub-inspection region (S110) is shownin detail in the flowchart of FIG. 8. The inspection process of asub-inspection region from the second time (S120 to S1N0) is the same asthe inspection process of the first sub-inspection region (S110). Theinspection process of the first sub-inspection region (S110) includes amultibeam irradiation process (S111), a frame image creation process(S112), a frame image comparison process (S113), determination of adifference in beam intensity (S114), and a detection pixel sensitivityadjustment process (S115).

<Multibeam Irradiation Process (S111)>

The multibeam irradiation process is a process in which sub-inspectionregions of the region to be inspected X are irradiated with themulti-primary electron beams 202 so as to be scanned. A different beamof the primary electron beams 202 is irradiated for each scanningregion. The multi-secondary electron beams 203 emitted from the regionto be inspected X are led to the multi-detector 176.

<Frame Image Creation Process (S112)>

The frame image creation process (S112) is a process in which a frameimage is created from the secondary electron beam 203 that has entered adetection pixel different for each scanning region of the sub-inspectionregion. For example, the first secondary electron beam 203 emitted fromthe first scanning region A1 enters the first detection pixel so that ananalogue signal is generated. The analogue signal is treated with signalprocessing in the detector 153 and a digital signal is generated. Thegenerated digital signal is temporarily stored in the pattern memory154. The digital signal stored in the pattern memory 154 is used forcreation of image data (first frame image C1) in the inspection imagecreation unit 140. The created first frame image C1 is stored in thememory 134, for example. As for other scanning regions, frame images arecreated in the same manner and stored in the memory 134.

<Frame Image Comparison Process (S113)>

In this process, luminance differences of the overlapping regions (D1 toD12) among the frame images are compared with each other. For example,from a difference between a luminance average (D1-1) of the overlappingregion D1 of the first frame image C1 and a luminance average (D1-2) ofthe overlapping region D1 of the second frame image C2, a change in adifference in intensity between the first primary electron beam 202after calibration and the second primary electron beam 202 irradiated onthe second scanning region A2 can be obtained.

As for other frame image regions, the difference in beam intensity canbe obtained in the same manner through comparison of overlapping regionsof the frame images. In the frame image comparison process, comparisonof gradation values of frame images, frame image histograms, and thelike can be performed.

In the embodiment, the comparison process in a unit of sub-inspectionregion and sub-inspection region image according to the scanning regionsof the multibeam is explained. However, in order to completely fill theinspection region image Y, the sub-inspection regions (S110-S1N0) areoverlapped with each other so as to prevent inspection omission.Therefore, a relation of the sub-inspection regions and overlapping inthe sub-inspection regions overlapping of which has been explainedapplies to a relation with the adjacent sub-inspection regions. Forexample, on a right side of A3, there is a portion overlapping with A1of the next sub-inspection region. Using this, comparison date betweenbeams for A1 and A3 can be obtained. For convenience of explanation,overlapping regions among the sub-inspection regions will be omitted,but information obtained according to this can also be used in the samemanner.

<Process of Determination of Difference in Beam Intensity (S114)>

In the process of determination of a difference in beam intensity (S114)is a process in which it is determined whether a difference in beamintensity obtained in the frame image comparison process (S113) is equalto or more than a threshold. This determination can be made in thecomparison unit 141. For example, when it is determined that thedifference in beam intensity is equal to or more than the threshold, thesensitivity of the detection pixel is adjusted in the detection pixelsensitivity adjustment process (S115). The difference in beam intensityin adjacent overlapping frame image regions is taken into considerationwhen it is determined whether the difference in beam intensity is equalto or more than the threshold. As a result, for example, when thedifference in beam intensity is less than the threshold, the sensitivityof the detection pixel is not adjusted, the inspection process of thefirst sub-inspection region (S110) ends, and the inspection process ofthe second sub-inspection region (S120) is performed in the same manneras the inspection process of the first sub-inspection region (S110).When the number of sub-inspection region is N, the inspection process isperformed until the inspection process of the N-th sub-inspection region(S1N0).

<Detection Pixel Sensitivity Adjustment Process (S115)>

The detection pixel sensitivity adjustment process (S115) is a processin which when it has been determined that the difference in beamintensity is equal to or more than the threshold in the process ofdetermination of a difference in beam intensity (S114), the detectionsensitivity of detection pixels corresponding to the primary electronbeams 202 between which there is a difference in beam intensity. First,the difference in beam intensity is obtained in the comparison unit 141,and an adjustment value of the detection sensitivity is obtained inconsideration of the difference in beam intensity in the sensitivityadjustor 142. The sensitivity adjustor 142 then makes a correction onlyfor the adjustment value from which the signal processing condition inthe detector 153 has been obtained. Through changing of the signalprocessing condition of the detector 153 for each inspection pixel, whenthe next sub-inspection region is inspected, a frame image for which thedifference in beam intensity during the previous inspection has beencorrected can be obtained. This means that since the processingcondition for acquiring the frame image in real time is changed, theinspection is performed under a condition in which the change in thebeam intensity generated from the beginning of the inspection to the endof the inspection has been corrected. If the signal processing is notperformed under an appropriate condition according to the beamintensity, the gradation value of the image may be too high or too low.Such an image whose gradation value is inappropriate as described abovecannot be easily corrected to be an image appropriate for defectdetection and the like even after being treated with the imageprocessing. In the embodiment, a correction is made in real time evenwhen a change occurs in the beam intensity. Therefore, an image moreappropriate for defect inspection and the like can be acquired.

<Inspection Image Creation Process (S201)>

The inspection image creation process (S201) is a process in which theinspection region image Y is created through overlapping and joining ofthe frame images acquired through an inspection of the sub-inspectionregions, the sub-inspection region images, or the frame images and thesub-inspection region images. The processing of overlapping and joiningof the images is performed in consideration of positional deviation. Inthe inspection image creation process (S201), processing and the likeare performed in the inspection image creation unit 140. The inspectionregion image Y is stored in the memory 134 and/or the storage device131.

<Reference Image Creation Process (S202)

The reference image creation process (S202) is a process in which areference image to be compared with the inspection region image Y iscreated. Processing and the like for reference image creation areperformed in the reference image creation unit 144. When a so-called dieto die inspection is performed, an adjacent inspection image of anidentical pattern portion is used as a reference image. Moreover, when aso-called die to database inspection is performed, a reference image iscreated from a design pattern, for example. The reference image isstored in the memory 134 and/or the storage device 131.

Note that although omitted in the embodiment, the reference image when adie to die inspection is performed is also acquired in the same processas the inspection image generation described above.

<Comparison Process (S203)>

The comparison process (S203) is a process in which the inspectionregion image Y is compared with the reference image so as to detect adefect. In the comparison process (S203), processing and the like areperformed in the comparison unit 141. A defect detection parameter isused to detect a defect from a difference between the inspection regionimage Y and the reference image. Detected defect information is storedin the storage device 131.

According to the inspection method of the embodiment, the difference inbeam intensity can be obtained in real time during the inspection, andan inspection image can be acquired under a condition considering thedifference in beam intensity.

Second Embodiment

A second embodiment is a modified example of the first embodiment. Inthe second embodiment, in the comparison unit 141, for example, in aframe image comparison process (S113) for comparison among the firstframe image C1, the second frame image C2, and the reference image, anda defect detection process (S116), defect detection result informationof each of the frame images in the overlapping region D1 is obtained,and this defect information is used to adjust the defect detectionparameter. This means that the second embodiment is different from thefirst embodiment in that at the time of a defect inspection of thesub-inspection region, a difference in defect information of theoverlapping region of each frame is used to adjust the defect detectionparameter.

In the comparison unit 141, the overlapping frame image region of theframe image is compared with the reference image. For example, in a casewhere when the first overlapping frame image region D1 of the firstframe image is compared with the reference image, a defect is detected,and when the first overlapping frame image region D1 of the second frameimage C2 is compared with the reference image, no defect is detected,the defect detection parameter is adjusted. When it cannot be determinedthat defect detection of either the first frame image C1 or the secondframe image C2 cannot be normally performed, for example, it ispreferred that the third frame image C3 partially overlapping with thesecond frame image C2 in the second overlapping frame image region D2 iscompared with the second frame image C2. When defect detection isperformed in the second overlapping frame image region D2 by thiscomparison, determination of whether or not the defect of the secondframe image C2 has been correctly detected is highly reliable. When acomparison of other overlapping frame image regions is performed aplurality of times, the defect detection parameter can be highlyaccurate.

The comparison unit 141 inspects the first sub-inspection region, forexample, and based on the difference in beam intensity, for example,adjusts the detection sensitivity of the first detection pixel and/orthe second detection pixel. Moreover, the comparison unit 141 adjuststhe defect detection parameter from the inspection of the firstsub-inspection region, inspects a second sub-inspection region, andcompares a frame image created by the first detection pixel whosedetection sensitivity has been adjusted and the secondary electron beamthat has entered the second detection pixel with the reference image soas to obtain the adjusted defect detection parameter. The comparisonunit 141 can detect a defect of the region to be inspected X using thisadjusted defect detection parameter, and further adjust the defectdetection parameter.

FIG. 9 shows a flowchart of the second embodiment. An inspection methodaccording to the second embodiment includes a calibration process(S101), inspection processes of sub-inspection regions (S110 to S1N0),and a reference image creation process (S202). In the first embodiment,the reference image creation process (S202) is performed before thecomparison process (S203). However, in the second embodiment, processingand the like of the reference image creation process (S202) areperformed before the inspection process of the first sub-inspectionregion (S110).

FIG. 10 shows a flowchart of the inspection process of the firstsub-inspection region according to the second embodiment. Note that inthe same manner as the first embodiment, the flowchart shown in FIG. 10is applicable to inspection processes of other sub-inspection regions.Processes other than the inspection processes of sub-inspection regions(S110 to S1N0) are common to the first embodiment and the secondembodiment. Explanations of common processes will be omitted.

<Inspection Processes of Sub-Inspection Regions (S110 to S1N0)>

The inspection process of the first sub-inspection region (S110) of thesecond embodiment includes a multibeam irradiation process (S111), aframe image creation process (S112), the frame image comparison process(S113), determination of a difference in beam intensity (S114), adetection pixel sensitivity adjustment process (S115), the defectdetection process (S116), a defect comparison process (S117), and adefect detection parameter adjustment process (S118). Processes otherthan the defect detection process (S116), the defect comparison process(S117), and the defect detection parameter adjustment process (S118) arecommon to the first embodiment and the second embodiment. Explanationsof common processes will be omitted. Note that the defect detectionprocess (S116), the defect comparison process (S117), and the defectdetection parameter adjustment process (S118) may be performed in theinspection processes of all the sub-inspection regions, or may beperformed in the inspection processes of some sub-inspection regions.The defect detection process (S116), the defect comparison process(S117), and the defect detection parameter adjustment process (S118) area group of processes, and these processes are continuously processed.Processing and the like of the processes of the group may be performedconcurrently with the process of determination of a difference in beamintensity (S114), or the processing and the like may be performed eitherbefore or after the process of determination of a difference in beamintensity (S114).

<Defect Detection Process (S116)>

In this process, frame images acquired in the inspection processes ofthe first to the N-th sub-inspection regions (S110 to S1N0) are comparedwith the reference image so as to perform defect detection of the frameimages in the same manner as the comparison process (S203).

<Defect Comparison Process (S117)>

The defect comparison process (S117) is a process in which, in frameimages having a common overlapping region in the defect detectionprocess (S116), defect information of each of the frame images iscompared, and a combination of one frame image in which a defect hasbeen detected and another frame image in which no defect has beendetected is extracted. In the defect comparison process (S117),processing and the like are performed in the comparison unit 141. Whenframe images, one of which has a detected defect and another of whichhas no detected defect, have been found, it is further determinedwhether a part that is not actually a defect has been detected as adefect in the one of the frame images, and whether no defect has beendetected in the other one of the frame images although there has been adefect. The adjustment of the defect detection parameter includes anadjustment of defect detection algorithm.

Even when a defect is detected in the same position of the overlappingregion in both of the adjacent frame images, if there is a difference inthe defect information due to a defect detection method such as defectintensity and a defect size, the difference can be used for adjustmentof the defect detection parameter as with defect presence/absenceinformation.

<Defect Detection Parameter Adjustment Process (S118)>

The defect detection parameter adjustment process (S118) is a process inwhich the defect detection parameter is adjusted from the defectinformation of the overlapping frame image region of the combination ofthe frame images extracted in the defect comparison process (S117). Inthe defect detection parameter adjustment process (S118), processing andthe like are performed in the comparison unit 141. For example, when apart that is not actually a defect has been detected as a defect (falsedefect) in one of the frame images, the defect detection parameter isadjusted so as not to defect the part, which has been detected as thedefect, as a defect. Moreover, for example, the defect detectionparameter is adjusted so as to defect a part that has not been detectedas a defect in the other one of the frame images although there has beena defect.

According to the inspection method of the embodiment, the defectdetection parameter is adjusted in the inspection processes ofsub-inspection regions (S110 to S1N0), and thus the accuracy of thefinal defect detection can be enhanced.

Third Embodiment

A third embodiment is a modified example of the first embodiment. Thethird embodiment is different from the first embodiment in that at leastone kind of image selected from a group including a frame image, asub-inspection region image, and an inspection image is corrected in theimage corrector 143. For example, using an image correction parameterobtained from a difference in beam intensity, a gradation value of thefirst frame image C1 and/or a gradation value of the second frame imageC2 is corrected in the image corrector 143. In the image corrector 143,an image is corrected with an algorithm considering the difference inbeam intensity. Settings of the detector 153 are adjusted according thedifference in beam intensity in real time. However, an image for whichthe difference in beam intensity has been obtained is an image that hasbeen inspected under a condition not considering the difference in beamintensity. Therefore, the image correction parameter is obtained fromthe obtained difference in beam intensity, and the image is corrected soas to eliminate (decrease) an influence of the difference in beamintensity. Any of a frame image, a sub-inspection region image formed ofjoined frame images, and the inspection region image Y formed of joinedsub-inspection region images can be corrected. Images obtained throughadjustment of the detector so as to compensate changes with time in thedifference in beam intensity do not have such a large difference in beamintensity. Accordingly, when the obtained images are slightly corrected,a correction can be made so as to eliminate (decrease) an influence ofthe difference in beam intensity. Therefore, in the point of view ofpost-processing of the images, the inspection apparatus of theembodiment is suitable.

FIG. 11 shows a flowchart of the third embodiment. An inspection methodaccording to the third embodiment includes a calibration process (S101),inspection processes of sub-inspection regions (S110 to S1N0), aninspection image creation process (S201), a reference image creationprocess (S202), a comparison process (S203), and an image correctionprocess (S301). In the third embodiment, a process is performed in whichat least one kind of image selected from a group including a frameimage, a sub-inspection region image, and the inspection region image Yis corrected. Processes other than the image correction process (S301)are common to the first embodiment. Explanations of common processeswill be omitted.

<Image Correction Process (S301)>

The image correction process (S301) is a process in which at least onekind of image selected from a group including a frame image, asub-inspection region image, and the inspection region image Y iscorrected based on information of the difference in beam intensity. Inthe image correction process (S301), processing and the like areperformed in the image corrector 143. According to an image to becorrected, order of performing the processing and the like of the imagecorrection process (S301) can be arbitrarily changed. It is preferredthat the image correction process (S301) is performed before thecomparison process (S203) in which defect detection is performed so thatthe image has been corrected when defect detection is performed, andthus the accuracy of defect detection is enhanced.

When a frame image is corrected, for example, the processing and thelike of the image correction process (S301) can be performed in theinspection process of each sub-inspection region. When a sub-inspectionregion image is corrected, the processing and the like of the imagecorrection process (S301) can be performed after the sub-inspectionregion image formed of overlapped and joined frame images is acquired.When the inspection region image Y is corrected, the processing and thelike of the image correction process (S301) can be performed between theinspection image creation process (S201) and the comparison process(S203). In any case, frame images can be substantially corrected.

FIG. 12 shows a flowchart of an inspection process of a firstsub-inspection region according to the third embodiment. Note that inthe same manner as the first embodiment, the flowchart shown in FIG. 12is applicable to inspection processes of other sub-inspection regions(S120 to S1N0). Processes other than the inspection processes ofsub-inspection regions (S110 to S1N0) are common to the first embodimentand the second embodiment. Explanations of common processes will beomitted.

In the image correction process (S301) whose processing is performed inthe inspection process of a sub-inspection region, for example, when agradation value of the third overlapping frame image region D3 of thefirst frame image C1 is higher than that of the third overlapping frameimage region D3 of the fourth frame image C4, the gradation value of theimage of the first frame image C1 is lowered or the gradation value ofthe fourth frame image C4 is increased using a correction algorism basedon the difference in beam intensity.

Fourth Embodiment

In a fourth embodiment, a correction value corresponding to a differencein beam intensity is obtained from an overlapping portion of acquiredframe images, and the correction value is applied to a gradation valueof the image in each frame image to detect a defect. Even when detectionsensitivity is not adjusted based on the difference in beam intensity,defect detection considering the difference in beam intensity can beperformed. Processing of defect detection of the fourth embodiment canbe adopted to the inspection apparatus (method) of the first to thethird embodiments.

In the first embodiment, in the frame image comparison process (S113),the difference in beam intensity is obtained from a difference ofluminance averages of an overlapping region D of two frame images C, andthe detection sensitivity is adjusted from the difference in beamintensity. In the fourth embodiment, in the same manner as the firstembodiment, a difference in beam intensity (offset) is obtained from anoverlapping region of frame images. Then, a luminance offset, which is adifference in luminance resulting from the difference in beam intensityin the overlapping region, is obtained. Using the luminance offset,defect detection is performed with a correction sensitivity parameterobtained through correction of a threshold of defect detection. Throughperforming of defect detection using the correction sensitivityparameter, highly reliable defect detection can be performed even when achange occurs in the beam intensity. Hereinafter, defect detectionconsidering the difference in beam intensity will be explained using anexample of the first frame image C1 and the second frame image C2.

When the average luminance of the overlapping region D1 of the firstframe image C1 is F_(C1) and the average luminance of the overlappingregion D1 of the second frame image C2 is F_(C2), ΔF_(C1C2)(=F_(C2)−F_(C1)), which is a luminance offset of the first frame imageC1 and the second frame image C2, is obtained.

When a pixel B, which is common to the first frame image C1 and thesecond frame image C2, is a defect candidate, defect detection of thedefect candidate is performed. FIG. 13 shows schematically the pixel B,which is common to the first frame image C1 and the second frame imageC2. First, a luminance aF_(ref) of the pixel B of a reference image, aluminance aF_(C1) of the pixel B of the first frame image C1, and aluminance aF_(C2) of the pixel B of the second frame image C2 areobtained. Then, E1 (=aF_(ref)−aF_(C1)), which is a luminance differenceof a defect candidate of the first frame image C1, and E2(=aF_(ref)−aF_(C2)), which is a luminance difference of a defectcandidate of the second frame image C2, are obtained. The luminancedifferences E1 and E2, and the luminance offset ΔF_(C1C2) satisfy arelation of E2=E1+ΔF_(C1C2).

In a case where a defect is determined when the luminance difference islarger than a threshold Th of defect detection, if an evaluation is madewithout considering the luminance offset, defect detection is affectedwhen the luminance offset ΔF_(C1C2) is large, for example. For example,when the luminance offset ΔF_(C1C2) is a positive value, in other words,when the luminance of the overlapping region D1 of the second frameimage C2 is higher than the luminance of the overlapping region D1 ofthe first frame image C1, a relation of E1<Th<E2 may be satisfied. Inthis case, if the difference in beam intensity is not taken intoconsideration, it is determined that the first frame image C1 has nodefect and the second frame image C2 has a defect. In the fourthembodiment, during the defect detection of the second frame image C2,determination is made using Thn (=Th+ΔF_(C1C2)), which is a correctionsensitivity parameter obtained through correction of the threshold Th bythe luminance offset ΔF_(C1C2). When the correction sensitivityparameter Thn is compared with the luminance difference E2 of the secondframe image C2, E2<Thn is satisfied, and it is determined that thesecond frame image C2 has no defect as with the first frame image C1.When the luminance offset ΔF_(C1C2) is a negative value, in other words,when the luminance of the overlapping region D1 of the second frameimage C2 is lower than the luminance of the overlapping region D1 of thefirst frame image C1, the luminance difference E1 of the first frameimage C1 is compared with the correction sensitivity parameter Thn(=Th+ΔF_(C1C2)) obtained through correction of the threshold Th by theluminance offset ΔF_(C1C2) to perform defect detection.

When the luminance offset ΔF_(C1C2) is caused by the difference in beamintensity, defect detection is performed considering the luminanceoffset ΔF_(C1C2) so as to perform highly reliable defect detectionconsidering the difference in beam intensity. In frame images other thanthe overlapping region D1, highly reliable defect detection can beperformed considering the luminance offset ΔF_(C1C2).

In the first embodiment, since the processing condition of the detector153 is adjusted based on the difference in beam intensity when the nextsub-inspection region is inspected, the detected difference in beamintensity corresponds to changes in the beam intensity with time. In thethird embodiment, since an inspection image in which the beam intensityhas changed is corrected based on the difference in beam intensity, theaccuracy of defect detection is further enhanced.

Each “unit” described above includes hardware, software, and acombination of hardware and software.

The embodiments have been explained above with reference to specificexamples. The embodiments described above are merely examples, and arenot limited. In addition, constituent elements of each embodiment may becombined as appropriate.

Although in the embodiments, descriptions of parts and the like notdirectly required for the explanation of the present invention such asthe configuration of the multibeam inspection apparatus, themanufacturing method thereof, and the multibeam inspection method areomitted, the required configurations of the multibeam inspectionapparatus and the multibeam inspection method may be appropriatelyselected and used. All other multibeam inspection apparatuses andmultibeam inspection methods that include elements of the presentinvention and can be appropriately designed or changed by those skilledin the art are within the scope of the present invention. The scope ofthe present invention is defined by the scope of the claims and thescope of the equivalents thereof.

What is claimed is:
 1. A multibeam inspection apparatus comprising: astage on which an object to be inspected is capable to be mounted, amultibeam column that irradiates the object to be inspected withmulti-primary electron beams, and a multi-detector including a firstdetection pixel that receives irradiation of a first secondary electronbeam emitted after a first beam scanning region of the object to beinspected is irradiated with a first primary electron beam of themulti-primary electron beams and a second detection pixel that receivesirradiation of a second secondary electron beam emitted after a secondbeam scanning region adjacent to the first beam scanning region of theobject to be inspected and overlapping with the first beam scanningregion is irradiated with a second primary electron beam adjacent to thefirst primary electron beam of the multi-primary electron beams; acomparison unit that obtains a difference in beam intensity between thefirst primary electron beam and the second primary electron beam bycomparing overlapping portions of a first frame image acquired throughentering of the first secondary electron beam into the first detectionpixel and a second frame image acquired through entering of the secondsecondary electron beam into the second detection pixel; and asensitivity adjustor that adjusts detection sensitivity of the firstdetection pixel and/or the second detection pixel so as to correct thedifference in beam intensity, wherein the comparison unit compares anoverlapping frame image region in which the first frame image and thesecond frame image overlap with each other with a reference image todetect a defect of the object to be inspected and obtain defectinformation, and adjusts a defect detection parameter using the defectinformation.
 2. The multibeam inspection apparatus according to claim 1,further comprising: an image corrector that corrects a gradation valueof the first frame image and/or a gradation value of the second frameimage using a correction value obtained from the difference in beamintensity.
 3. The multibeam inspection apparatus according to claim 1,wherein the comparison unit that detects a defect of the object to beinspected by comparing an image formed of the first frame image and thesecond frame image overlapped with each other and joined together with areference image.
 4. The multibeam inspection apparatus according toclaim 1, wherein the comparison unit detects a defect of the object tobe inspected by comparing an image formed of joined frame images thathave been created from secondary electron beams that have entered thefirst detection pixel and the second detection pixel for which thedetection sensitivity has been adjusted with a reference image, andusing the defect detection parameter that has been adjusted.
 5. Themultibeam inspection apparatus according to claim 2, wherein thecomparison unit detects a defect of the object to be inspected using animage that has been corrected in the image corrector.
 6. The multibeaminspection apparatus according to claim 1, wherein an inspection imageis acquired through scanning of the first beam scanning region and thesecond beam scanning region of the object to be inspected by themulti-detector for which the detection sensitivity has been adjusted. 7.A multibeam inspection apparatus comprising: a stage on which an objectto be inspected is capable to be mounted, a multibeam column thatirradiates the object to be inspected with multi-primary electron beams,and a multi-detector including a first detection pixel that receivesirradiation of a first secondary electron beam emitted after a firstbeam scanning region of the object to be inspected is irradiated with afirst primary electron beam of the multi-primary electron beams and asecond detection pixel that receives irradiation of a second secondaryelectron beam emitted after a second beam scanning region adjacent tothe first beam scanning region of the object to be inspected andoverlapping with the first beam scanning region is irradiated with asecond primary electron beam adjacent to the first primary electron beamof the multi-primary electron beams; a comparison unit that obtains adifference in beam intensity between the first primary electron beam andthe second primary electron beam by comparing overlapping portions of afirst frame image acquired through entering of the first secondaryelectron beam into the first detection pixel and a second frame imageacquired through entering of the second secondary electron beam into thesecond detection pixel; a sensitivity adjustor that adjusts detectionsensitivity of the first detection pixel and/or the second detectionpixel so as to correct the difference in beam intensity; and an imagecorrector that corrects a gradation value of the first frame imageand/or a gradation value of the second frame image using a correctionvalue obtained from the difference in beam intensity.
 8. The multibeaminspection apparatus according to claim 7, wherein the comparison unitthat detects a defect of the object to be inspected by comparing animage formed of the first frame image and the second frame imageoverlapped with each other and joined together with a reference image.9. The multibeam inspection apparatus according to claim 7, wherein thecomparison unit detects a defect of the object to be inspected using animage that has been corrected in the image corrector.
 10. The multibeaminspection apparatus according to claim 7, wherein an inspection imageis acquired through scanning of the first beam scanning region and thesecond beam scanning region of the object to be inspected by themulti-detector for which the detection sensitivity has been adjusted.